Carotenoids are natural pigments useful as feed additives, food additives, pharmaceutical ingredients and so on. Carotenoids include astaxanthin, canthaxanthin, zeaxanthin, β-cryptoxanthin, lycopene, β-carotene, phoenicoxanthin, adonixanthin, echinenone, asteroidenone and 3-hydroxyechinenone. Among them, astaxanthin is useful as a body color improver for cultured fish including salmon, trout and red sea bream and/or useful as a feed additive such as a color improver for poultry egg yolk. Astaxanthin is also industrially valuable as a safe and natural food additive or health food material. As in the case of astaxanthin, adonixanthin and phoenicoxanthin are also expected for use as feed additives, food additives, pharmaceutical ingredients or the like once their industrial production has been established. In addition, β-carotene is used as a feed additive, a food additive, a pharmaceutical ingredient or the like, canthaxanthin is used as a feed additive, a food additive, a cosmetic ingredient or the like, and zeaxanthin is used as a food additive, a feed additive or the like. Further, lycopene, echinenone, β-cryptoxanthin, 3-hydroxyechinenone, asteroidenone and others are also expected for use as feed additives, food materials or the like. For production of these carotenoids, chemical synthesis, extraction from natural products, microbial production or other techniques are known.
For chemical synthesis of astaxanthin, conversion from β-carotene (Non-patent Document 1: Pure Appl. Chem., 57, 741, 1985) and synthesis from C15 phosphonium salt (Non-patent Document 2: Helv. Chim. Acta, 64, 2436, 1981) are known. Astaxanthin produced by these chemical synthesis techniques is commercially available as a feed additive. Astaxanthin can also be extracted from fish (e.g., red sea bream, salmon) and crustaceans (e.g., shrimp, crab, krill) because astaxanthin is found in these organisms.
For microbial production of astaxanthin, there are reports of culture in green algae Haematococcus pluvialis (Patent Document 1: JP 2007-97584 A), fermentation in red yeast Phaffia rhodozyma (Patent Document 2: JP H11-69969 A), and fermentation in bacteria belonging to the genus Paracoccus (hereinafter also referred to as “Paracoccus sp.”). Examples of astaxanthin-producing bacteria belonging to the genus Paracoccus include strains E-396 and A-581-1 (Patent Document 3: JP H7-79796 A and Non-patent Document 3: International Journal of Systematic Bacteriology (1999), 49, 277-282). Other astaxanthin-producing bacteria belonging to the genus Paracoccus include Paracoccus marcusii strain MH1 (Patent Document 4: JP 2001-512030 A), Paracoccus haeundaensis strain BC74171 (Non-patent Document 4: International Journal of Systematic and Evolutionary Microbiology (2004), 54, 1699-1702). Paracoccus sp. strain N-81106 (Patent Document 5: JP 2007-244205 A), Paracoccus zeaxanthinifaciens (Non-patent Document 5: International Journal of Systematic and Evolutionary Microbiology (2003), 53, 231-238) and Paracoccus sp. strain PC-1 (Patent Document 6: WO 2005/118812), etc.
However, the above techniques for carotenoid production have some problems. For example, chemical synthesis would make an unfavorable impression on consumers in terms of safety. Likewise, extraction from natural products requires high production costs. Moreover, production in green algae or yeast not only provides low productivity, but also makes difficult carotenoid extraction because of their rigid cell walls.
In contrast, bacteria belonging to the genus Paracoccus are advantageous, e.g., in having high growth rate and in achieving high productivity and easy extraction of carotenoids, and some reports have been issued for methods of their culture. JP 2007-143492 A (Patent Document 7) discloses a method in which an iron salt is added during culture, while JP 2008-167665 A (Patent Document 8) discloses a method in which the carbon source concentration is limited. However, these methods are not practical for commercial or industrial purposes because an expensive yeast extract is used in a large amount as a material of the medium.